Using the Slurry-bed Reactor

FIELD OF THE INVENTION

The present invention relates to the field of chemical engineering. In particular, it relates to a novel slurry-bed reactor for enhancing particle suspension, liquid-solid mixing, heat transfer and mass transfer through external slurry circulation. The present invention further relates to a method for conducting the slurry-bed reaction using the slurry-bed reactors.

BACKGROUND

With oil resources decreasing worldwide, development of alternative energy technology has been paid more and more attention. Products such as cleaner fuel and wax with high quality can be produced by producing synthesis gas from carbon and hydrogen-containing raw materials such as coal, natural gas, and biomass, processing the synthesis gas with water-gas shift and purification, and using the synthesis gas as the raw material to produce hydrocarbons through Fischer-Tropsch synthesis technology, and meanwhile producing the byproducts of oxygenated compounds, then adopting mature petroleum processing technology. The core of the technical path is Fischer-Tropsch synthetic technology.

There are two types of catalysts which are used in liquid fuel production by Fischer-Tropsch synthesis using coal or natural gas as raw materials. One type is iron-based catalysts and the other is cobalt-based catalysts. Iron-based catalysts need to be replaced every 70-100 days due to poor stability. The frequent replacement of the catalysts limited the development of this technology. With better stability, cobalt-based catalysts could avoid frequent replacement of the catalysts and can be used in Fischer-Tropsch synthesis in fixed-bed reactors. However, a Fischer-Tropsch synthesis reaction is an exothermal reaction. A Fischer-Tropsch synthesis in a fixed-bed reactor is prone to problems such as hotspot and coking, which makes it difficult for amplification. Later, Fischer-Tropsch synthesis reactors have been developed as circulating fluidized beds, fixed fluidized beds, and slurry beds. However, in a circulating fluidized bed, the fluidization process is hard to control; the utilization rate of catalysts is low with serious attrition; and the production capacity is still low. A fixed fluidized bed has simple structure and can overcome the problems of low catalyst utilization rate and serious attrition. However, it is applied only to high-temperature Fischer-Tropsch synthesis rather than the production of high value-added heavy fraction such as clean diesel and wax.

Comparing with conventional gas-solid fluidized beds, the bubbling slurry-bed reactor technology, which comprises the gas-liquid-solid tri-phases, possesses advantages in many aspects. First, the reaction heat can be effectively removed and the reaction temperature can still be effectively controlled using a highly active catalyst (i.e. a high yield catalyst) so that the reactor is relatively easy to amplify and realize single-series large-scale industrialized production. Second, the reactor is approximately operated isothermally and the high value-added liquid hydrocarbon products such as clean diesel and heavy wax can be produced as the main products by selecting suitable catalysts and reaction temperature. Third, the operation environment of catalysts can be improved and thus the attrition of catalysts can be deceased. The average life of catalysts is well under control by regular replacement of catalysts. Therefore, slurry-bed reactor technology becomes an important technology in producing diesel and wax as the main products by Fischer-Tropsch synthesis. In addition to the Fischer-Tropsch synthesis process, slurry-bed reactors also have application potential in other reaction processes involving the gas-liquid-solid tri-phases.

A slurry-bed reaction relates to mass transfer, heat transfer and reaction among gas-liquid-solid tri-phases. Key to the reaction is the microcosmically well-distributed particle suspension and uniform liquid-solid mixing. Otherwise, a slurry-bed reactor may have the problem of reaction hotspot similar to a fixed-bed reactor due to agglomeration of particles, and therefore affect heat stability of the whole operation of the reactor. Being aware of this fact, the design of a slurry-bed reactor should meet two basic requirements. First, in order to maintain the features of a slurry bed, the catalysts should be prepared as fine particles with sufficient mechanical strength through particular forming process to ensure well-distributed suspension in liquid slurry materials. Second, the reactor diameter should be selected to make sure that the raw material gas is able to get through the slurry bed layer with bubbling at a certain superficial gas velocity. It will cause sedimentation and agglomeration of catalyst particles if gas materials pass through the slurry-bed layer at a velocity which is too slow. On the other hand, it will cause serious tail gas entrainment and particle entrainment if the gas velocity is too high.

However, comparing with the liquid medium, the density of gas medium is limited. The superficial gas velocity of a bubbling slurry bed is also limited to a limited range so that the kinetic energy provided by the bubble with a certain gas velocity is also limited for particle suspension and enhancement of mass transfer and heat transfer. For the design of a slurry-bed reactor for a Fischer-Tropsch synthesis, one of the key technologies is still how to design the enhanced turbulence and suitable internal components to enhance the particle suspension and uniform liquid-solid mixing, as well as mass transfer, heat transfer and reaction among the three phases in the whole reactor.

Therefore, persons skilled in the art still desire to develop a slurry-bed reactor with improved particle suspension and liquid-solid mixing effects.

DETAILED DESCRIPTION OF THE INVENTION

In seeking to solve the aforementioned problems, the present invention provides a slurry bed reactor with good particle suspension and liquid-solid mixing effects and a method for using the reactor.

In one aspect of the present invention, a slurry-bed reactor is provided, and the slurry-bed reactor comprises: a reactor vessel, a plurality of descending pipes, a plurality of injectors and a gas distributor provided in the reactor vessel, a middle external circulation apparatus and/or a top external circulation apparatus, wherein the middle external circulation apparatus draws out at least a portion of slurry materials in the reactor vessel and at least a portion of the slurry materials is recycled back to the reactor vessel, the top external circulation apparatus draws out at least a portion of gas materials in the reactor vessel and at least a portion of the gas materials are recycled back to the reactor vessel, wherein the plurality of descending pipes are provided along the inner wall of the reactor vessel. The injectors are provided at different vertical height in a central region of the vessel with injector openings of injectors being directed upwardly or obliquely upwardly.

In an embodiment of the present invention, the height difference between the gas distributor and the nearest injector to the gas distributor is at least 1%, preferably at least 2.5%, of the height of the reactor vessel. In an embodiment of the present invention, the height difference between the gas distributor and the nearest injector to the gas distributor is no more than 20%, preferably no more than 10%, of the height of the reactor vessel.

In an embodiment of the present invention, the height difference between the nearest injector to the gas distributor and the farthest injector to the gas distributor is at least 40%, preferably at least 50%, of the height of the reactor vessel. In an embodiment of the present invention, the height difference between the nearest injector to the gas distributor and the farthest injector to the gas distributor is no more than 90%, preferably no more than 80%, of the height of the reactor vessel.

In an embodiment of the present invention, there is at least one injector located between the nearest injector to the gas distributor and the farthest injector to the gas distributor, and the injectors are evenly or unevenly spaced between each other in the vertical direction.

In an embodiment of the present invention, the middle external circulation apparatus comprises a liquid-solid separator and a circulation pump, preferably comprises a gas-liquid separator located outside of the reactor vessel. The top external circulation apparatus comprises a condenser, a gas-liquid separator and a circulation pump located outside of the reactor vessel of the present invention.

In an embodiment of the present invention, 2-10 groups of descending pipes are provided at different vertical height in the slurry-bed reactor, wherein each group of the descending pipes extends in the same vertical height, and is provided along the inner wall of the reactor vessel in a horizontally aligned manner. Corresponding descending pipes belonging to different groups align with each other in the vertical direction.

Another aspect of the present invention provides a method for conducting a slurry-bed reaction using the slurry-bed reactor of the present invention, the method comprises the following steps: i) gas reactants are supplied to the gas distributor. The gas ascends in the space in the reactor vessel and outside of the descending pipes after getting through the gas distributor and drives the ascending of slurry materials, and reacts in the presence of catalyst in the slurry materials; ii) the resulting gas materials carrying an amount of slurry materials ascend to the upper part of the reactor vessel. The resulting gas is drawn out by a top external circulation apparatus. Gas in the resulting gas materials and the slurry materials carried therein are separated, then at least a portion of the separated liquid materials are recycled back into the reactor vessel, preferably through the injectors spraying upwardly or obliquely upwardly; iii) optionally, at least a portion of slurry materials in the reactor vessel is drawn out by a middle external circulation apparatus, and liquid materials and solid materials in the slurry materials are separated, and at least a portion of the liquid materials is recycled back to the reactor vessel, preferably through the injectors spraying upwardly or obliquely upwardly; iv) a portion of the slurry materials flows into the descending pipes from the top opening of the descending pipes, and flows out from the bottom of the descending pipes, then ascends again in the space in the reactor vessel and outside of the descending pipes driven by the gas reactants, and repeat the foregoing steps (i)-(iv).

Another aspect of the present invention provides a method for conducting a slurry-bed reaction using a reactor comprising a reactor vessel including a slurry, the method comprises the following steps: i) supplying gas reactants feed to a gas distributor in the reactor vessel to drive upward movement of slurry and allowing the gas reactants feed to react in the slurry; ii) drawing out at least a portion of the resulting gas materials in the reactor vessel from the upper region of the vessel. Gas in the slurry materials and slurry carried therein are separated, then at least a portion of the separated liquid materials are recycled back to the reactor vessel, preferably through the injectors spraying upwardly or obliquely upwardly; iii) optionally, at least a portion of slurry materials in the reactor vessel is drawn out, and liquid materials and solid materials in the slurry materials are separated, and then at least a portion of the separated liquid materials is recycled back to the reactor vessel, preferably through the injectors spraying upwardly or obliquely upwardly; iv) passing a portion of the slurry materials into an upper opening of descending pipes, and out from a bottom opening of the descending pipes, into a lower region of reactor vessel.

In an embodiment of the present invention, in the aforementioned method for conducting slurry-bed reaction, the resulting gas materials are separated preliminarily in the reactor vessel to separate the slurry carried therein and the gas materials before the resulting gas materials are drawn out from the reactor vessel.

By the design of the present invention, the gas reactants and the liquid-solid materials ascend under the effect of the gas distributor in the reactor vessel on the ascending, reacting and forming the slurry materials in the ascending process. The slurry materials are at the place near the gas-liquid interface. The gas keeps ascending, entering into the top region of the reactor vessel. The slurry, with density increased, after the gas materials are removed, gets into the descending pipes from the top opening of the descending pipes, flows downwardly under its own gravity and flows out from the bottom opening of the descending pipes, then ascend again in the space in the reactor vessel and outside of the descending pipes driven by the gas reactants, forming a internal reacting circulation. At the same time, the middle external circulation apparatus and/or the top external circulation apparatus can draw out at least a portion of slurry materials and/or gas materials in the reactor vessel, conducting the gas-liquid, gas-solid, liquid-solid and gas-liquid-solid separation for the aforementioned slurry materials and/or gas materials, separating the usable liquid materials and recycling them externally back to the reactor vessel through the injectors, separating the usable gas materials and delivering them back to the reactor vessel through the gas distributor. The gas that is recycled back continues to react. The liquid (e.g. light hydrocarbons containing C5-C10) that is recycled back to the reactor vessel continues to provide the effect of stirring and suspending on the slurry. The aforementioned design facilitates the suspension of particles, mixing of liquid and solid, and heat transferring and mass transferring.

BRIEF DESCRITION OF THE DRAWINGS

Certain specific embodiments of the present invention will be described in more detail in combination with the drawings:

Figure 1 is a schematic diagram of an embodiment of the slurry-bed reactor of the present invention, wherein all the descending pipes are set up in the same layer.

Figure 2 shows a cross-sectional view of the descending pipe 28 in Figure 1.

Figure 3 is a schematic diagram of an embodiment of a slurry-bed reactor of the present invention, including three layers of descending pipe.

Figure 4 is a schematic diagram of an injector with a Venturi structure.

Figure 5 A and 5B are schematic diagrams of tubular-shape injectors with their opening surface having a plurality of pore shaped openings.

Figure 6A is a schematic diagram of a preferred spraying state of the tubular injector of the present invention.

Figure 6B is a schematic diagram of another preferred spraying state of the tubular injector of the present invention.

Figure 7 is a schematic diagram of the height L of the reactor vessel of the present invention and the height H of the gas-liquid interface.

Description of Reference Labels in the Drawings

1. Reactor vessel;

2. Gas-liquid interface;

3. Gas-liquid separation zone;

4. Condenser;

5. Gas-liquid separator ;

6. Liquid product;

7. Condensed liquid;

8. Tail gas;

9. Circulation gas;

10. Circulation pump;

1 1. Heater;

13A, 13B, 13C. Injectors;

28, 28A, 28B, 28C. Descending pipes;

16. Liquid-solid separator;

17. Slurry with depleted solid;

18. Pressure relief valve;

19. Gas-liquid separator ;

20. Tail gas;

21. Secondary liquid-solid separator;

22. Liquid product;

23. Circulation pump;

24. External circulation slurry with depleted solid; 25. Gas compressor;

26. Fresh gaseous reactant materials;

27. Gas distributor

101. Blocking component;

1 10. Opening surface

1 12. Open pore

EXAMPLES The "range" disclosed herein is in the form of lower limit and upper limit.

There can be one or more lower limits, and one or more upper limits, respectively. A given range is limited by selecting a lower limit and an upper limit. The selected lower limit and upper limit will determine the boundary of the specific range. The range limited by such way can be included or combined, i.e. any lower limit and any upper limit can be combined to form a range. For example, the range of "60-120 and 80-1 10" that is given by specific parameters can be understood to be 60-1 10 and 80-120. In addition, if a minimum value is 1 and 2, and a maximum value is 3, 4, and 5, the following range can thus be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. Unless otherwise specified, all of the embodiments and preferred embodiments described herein can be combined to obtain new technical solutions.

Unless otherwise specified, all of the technical features and preferred features described herein can be combined to obtain new technical solutions.

Unless otherwise specified, all of the steps described herein can be performed in the order as written or in a random order, preferably in the order as written. For example, a method comprises steps (a) and (b) means the method can comprise steps (a) and (b) in such order, or steps (b) and (a) in such order. For example, a method further comprising step (c) means step (c) can be added into the method in any order, for example, the method may comprise steps such as steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc. Figure 1 shows an embodiment of the slurry-bed reactor of the present invention. It can be found from the figure that the reactor includes two portions, i.e. the portion in the reactor vessel and the portion outside of the reactor vessel. The inside of the reactor vessel 1 includes a plurality of descending pipes 28, a plurality of injectors 13 (e.g. 13A, 13B) and a gas distributor 27. The reactor vessel 1 can contain slurry, which can be any slurry formed by dispersing solid materials into liquid materials. The outside of the reactor vessel 1 includes a middle external circulation apparatus that can be used for drawing out at least a portion of the slurry materials in the slurry materials beneath a gas-liquid interface 2 from the reactor vessel and recycling them externally and back into the reactor vessel 1, specifically to the injectors 13 A, 13B, and a top external slurry circulation apparatus that can be used for recycling externally at least a portion of the resulting gas materials to the reactor vessel 1, specifically to the injectors 13 A, 13B. The gas materials can include the gas reactants and the inert gas that does not react.

The gas reactant materials 26 can be delivered to the gas distributor 27 by any known automatically or manually controlled components such as pipes, valves, controlling component and so on. According to the requirements of a specific process, these components can further optionally comprise pumps, pressure component, decompressors, heating component, cooling component, detection component, etc. The gas reactant materials 26 that are delivered can comprise any gas materials that are required for a reaction process, for example, reactants, inert diluent gas, gas used for inactivating the reaction system to stop the reaction, etc. These gas materials can be mixed first, and then delivered to the reactor vessel 1 or multiple gas materials at a desired ratio can be delivered through a plurality of parallel pipes.

The gas distributor 27 can be any gas distribution means well-known in the art, for example, gas distribution plates containing a plurality of pores, gas distributors containing injector structures, etc.

As shown in Figure 3, the plurality of descending pipes 28 are provided uniformly along the inner wall of the reactor vessel 1 above the gas distributor 27. According to the size of the reactor and the specific reaction process, any number of the descending pipes 28 can be used. In an embodiment of the present invention, the reactor comprises 3-20 descending pipes, preferably 6-10 descending pipes, more preferably 8 descending pipes. Optionally, a blocking component 101 is provided at the lower opening of the descending pipe. The cross-section area of the block component 101 along the horizontal direction and facing the gas distributor 27 is generally larger than the cross-section area at the lower opening of the descending pipe, and thus prevents the direct entrance of up flow from the gas distributor 27 into the center descending pipe, and therefore affects the homogeneity and flowing performance of the slurry therein.

As shown in Figure 1, a plurality of injectors 13 (e.g. 13A and 13B) are provided at different height in the center of the reactor vessel 1. As shown in Figure 3, a plurality of injectors 13 (e.g. 13A, 13B and 13C) are provided at different height in the center of the reactor vessel 1. The reactor in the present invention can comprise 2-10 layers of injectors provided in different height, including 1-10 injectors 13 provided in a symmetrical manner in each layer. In another word, when there is only 1 injector in each layer, the injector is provided in the center along the longitudinal axis of the reactor. When there are more injectors, these injectors are provided in a central symmetrical manner around the longitudinal axis of the reactor. The opening direction of the injectors makes the liquid materials eject from the injectors in a straight upward or obliquely upward direction.

In the present invention, the height of the injectors is specifically defined. In one embodiment, the height difference between the gas distributor 27 and the nearest injector to the gas distributor 27 (e.g. injector 13B in Figure 1, injector 13C in Figure 3) is at least 1%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, preferably at least 2.5%, of the height L of the reactor vessel (the height L of the reactor vessel is the distance between the top sealing head and the bottom sealing head which is marked as L in the Figure 7), or is no more than 20%, such as 8% 9%, 10%, 1 1%, 12%, 13%, 14%, 15% or 20%, preferably no more than 10%, of the height L of the reactor vessel.

In an embodiment, the height difference between the nearest injector to the gas distributor 27 (e.g. injector 13B in Figure 1, injector 13C in Figure 3) and the farthest injector to the gas distributor 27 (e.g. injector 13A in Figure 1, injector 13A in Figure 3) is at least 40%, such as 40%, 45%, 50%, 55% or 60%, preferably at least 50%, of the height L of the reactor vessel. The height difference between the nearest injector to the gas distributor 27 (e.g. injector 13B in Figure 1, injector 13C in Figure 3) and the farthest injector to the gas distributor 27 (e.g. injector 13A in Figure 1 , injector 13A in Figure 3) is no more than 90%, such as 70%, 75%, 80%, 85% or 90%, preferably no more than 80%, of the height L of the reactor vessel.

In an embodiment, there is at least one injector located between the nearest injector to the gas distributor 27 and the farthest injector to the gas distributor 27, and the injectors are evenly or unevenly spaced between each other in the vertical direction.

In an embodiment of the present invention, when the slurry-bed reactor of the present invention is under normal working condition, the height from the gas distributor 27 to the gas-liquid interface 2 of the slurry materials (the height H of the gas-liquid interface is shown in Figure 7) is assumed as H, thus the height difference between the gas distributor 27 and the nearest injector to the gas distributor is 2%-20% H, preferably 5%~10% H. The remaining injectors are provided between the gas-liquid interface and the nearest injector to the gas distributor, preferably provided evenly spaced out in height.

In an embodiment of the present invention, the ejecting kinetic energy per unit volume of the slurry ejected from the injectors is 0.001-0.05 W/m ³ , preferably 0.002-0.005 W/m . In an embodiment of the present invention, the ejecting kinetic energy per unit volume of the slurry ejected from the injectors is at least 0.001 W/m ³ , 0.002 W/m ³ , 0.003 W/m ³ , 0.004 W/m ³ , 0.005 W/m ³ or 0.008 W/m ³ . In an embodiment of the present invention, the ejecting kinetic energy per unit volume of the slurry ejected from the injectors is no more than 0.01 W/m ^J , 0.02

W/m 3 , 0.03 W/m 3 , 0.04 W/m 3 or 0.05 W/m 3. In an embodiment of the present invention, the position of the injectors in the reactor vessel can be adjusted.

The injector 15 can be any type of injector. Figure 4 shows a schematic diagram of a Venturi injector that can be used as an injector of the present invention. The opening of this Venturi injector is provided upwardly. The internal diameter of the pipe near the opening is gradually narrowed and then gradually enlarged. Such change of internal diameter of the pipe will ensure the corresponding increase in pressure and flow velocity of the liquid getting through the Venturi tube, and thus provide stronger driving force for the ascending of slurry materials. Similarly, Figure 5A shows a tubular injector with a plurality of open pores on the top. The tubular injector can be used as injectors of the present invention. The opening surface 1 10 is pointed upwardly. The opening surface 1 10 has a plurality of open pores 1 12 as shown in Figure 5B. The other parts are closed. A plurality of open pores 1 12 as shown in the figure are provided on the opening surface 1 10 in a manner of central symmetry. However, they can also be provided in other manners as needed. The ejecting direction of the liquid ejected from the plurality of open pores 1 12 can be vertical to the opening surface 1 10 or oblique. In a most preferable embodiment, the ejecting direction of the liquid ejected from the plurality of open pores 1 12 is distributed in a cone shape by taking one point on the central axis of the tubular injector and beneath the ejection surface as the vertex, and taking the ejection surface as the bottom side as shown in Figure 6A. More preferably, the ejecting direction of the liquid is oblique with the same angle on the lateral side of the cone to ensure that the direction of liquid ejected from each open pore will not go through the vertex of said cone, which means liquid is ejected spiraling up as shown in Figure 6B. In a most preferable embodiment, the opening of the plurality of open pores 1 12 is convergent inwardly and directed obliquely upwardly, forming an angle of 45-90° with the horizontal plane, and an angle of 0-45° with the vertical direction. Such special setting can also provide stronger driving force for the descending of slurry materials in the center descending pipe.

Although the reactor shown in Figure 1 only comprises 1 layer of descending pipes, according to the specific characteristics such as specific reaction type, reaction system scale, reactor structure and etc, a plurality of layers of descending pipes can be selected. Figure 3 shows a reactor comprising 3 layers of descending pipes. The reactor shown in Figure 3 comprises 3 groups of descending pipes, and there are 3-20 descending pipes in each group, preferably 6-10 descending pipes, more preferable 8 descending pipes. Each group of descending pipes is provided in the same layer, extending in the vertical direction along the inner wall of the reactor vessel 1 of the same length. I.e., descending pipes of each layer are aligned with each other in horizontal direction, and sectional views of their horizontally disposed position are shown in Figure 2. Descending pipes belonging to different groups align with each other in the vertical direction, making the slurry materials go through the respective descending pipe smoothly and drop from the space nearby the gas-liquid interface 2 to the space above the gas distributor 27. The reactor in Figure 3 comprises 3 injectors, which are provided in almost the same way as those in Figure 1 , so the unnecessary details will not be given herein.

The reactor vessel 1 can be filled with slurry. For example, for a Fischer-Tropsch reaction, the slurry can be formed by solid materials such as the corresponding catalysts suspending in the materials such as liquid solvents, products, by-products, etc. Preferably, under the normal working condition, gas-liquid interface 2 of the slurry is higher than the height of the descending pipes and injectors, so that the latter are all submerged beneath the gas-liquid interface 2.

The middle external circulation apparatus and/or top external circulation apparatus are also provided outside of the reactor vessel 1. Either a middle external circulation apparatus or a top external circulation apparatus may be provided. Preferably, only the top external circulation apparatus is provided. Most preferably, both of the middle external circulation apparatus and top external circulation apparatus are provided. The middle external circulation apparatus comprises liquid-solid separator 16 located in the reactor vessel and the circulation pump 23. When the slurry materials that is recycled by the middle external circulation apparatus contains gas, the middle external circulation apparatus can further comprise gas-liquid separator 19, optionally further comprise secondary liquid-solid separator 21 and optional heater 1 1. Preferably, under the normal working condition of the slurry-bed reactor, the liquid-solid separator 16 is placed beneath the gas-liquid interface 2 for conducting solid-liquid separation and drawing a portion of slurry. The liquid-solid separator 16 can be one or more conventional filters. It can be also a liquid-solid cyclone separator. Preferably, the filtered slurry 17 with low global solid content is delivered to gas-liquid separator 19 by a pressure relief valve 18. The gas separated from liquid is directly discharged as tail gas 20 or delivered for post-processing process. Further solid-liquid separation or liquid-liquid separation is conducted in secondary liquid-solid separator 21 for the liquid to remove any gas. The valuable liquid reaction product 22 is removed from the reaction system. Then the remaining liquid, i.e. the external circulation slurry 24 with low solid content passes through circulation pump 23 and is heated to reaction temperature in optional heater 1 1 , and then sent back to the reactor vessel 1, specifically to the injectors 13A 13B and 13C, and thus complete the middle external circulation process of slurry. In this middle external circulation apparatus, the liquid-solid separator, gas-liquid separator, circulation pump and heater can be any suitable means well-known in the art. However, in a preferable embodiment, the circulation pump is preferably a circulation pump with open blade impeller. Such circulation pump is with strong particle wearable performance. Meanwhile, it is helpful for slowing down the particle attrition of catalysts.

The top external circulation apparatus comprises condenser 4, gas-liquid separator 5, circulation pump 10 and optional heater 1 1. Gaseous products or by-products are entrained with some liquid. Even the solid materials leave the gas-liquid interface 2 and ascend to gas-liquid separation zone 3, where a certain degree of gas-liquid or gas-solid separation is taken place, and then goes to the outside of reactor vessel 1, and condensed in condenser 4. Sufficient gas-liquid separation occurs in gas-liquid separator 5. The worthless components in the gas phase isolate is discharged as tail gas 8 or delivered to the other post-processing process. The unreacted gas raw materials are used as circulation gas 9 and re-delivered to gas distributor 27 after being mixed with fresh gas reactant materials compressed by gas compressor 25. A portion in the separated liquid components is discharged as certain liquid products 6. While recyclable liquid components (which is usually C ₅ -Ci ₀ light hydrocarbons) are used as external slurry circulation materials, pass through circulation pump 10 and are heated to desired reaction temperature in optional heater 1 1, and then sent back to injectors 13A 13B and 13C. In the present invention, the middle external circulation apparatus and the top external circulation apparatus may use the same heater (e.g. the one shown in Figure 1 and Figure 3). Alternatively, the middle external circulation apparatus and the top external circulation apparatus can each include a heater (not shown in the figures). In some embodiments of the present invention, the middle external circulation apparatus and the top external circulation apparatus each includes a heater. In such embodiments, the top external circulation apparatus can have the arrangements shown in Figure 1 and Figure 3; the middle external circulation apparatus needs to have a heater added at a position after the externally circulated slurry 24 with low solid content passes circulation pump 23 and before it returns back to injector 24.

In particular, the external circulation liquid of the present invention can be oil phase generated by despumation, condensation, phase separation and dehydration of the gas phase products from the top of the reactor. It can be also slurry phase beneath the slurry surface. However, either one can provide external circulation materials for the injectors. For example, only the top external circulation apparatus is used to provide external circulation materials or only the middle external circulation apparatus is used to provide external circulation materials. It is preferable to use top external circulation apparatus to provide external circulation materials.

By using a slurry-bed reactor as disclosed herein, the present invention provides a slurry-bed reaction method with improved material circulation and stability. In particular, the method can be conducted based on the following steps: first, gas reactants 26 such as synthesis gas are supplied to gas distributor 27, the gas reactants 26 are uniformly distributed or distributed according to a specific manner after getting through the gas distributor 27, the gas reactants ascend in the space in the reactor vessel 1 and outside of the center descending pipes 28 after getting through the gas distributor 27, and contact with the slurry materials contained in the vessel 1 during the ascending, and react in the presence of catalyst in the slurry materials. In addition, the ascending of the gas also brings ascending power to the slurry, and accordingly drives the ascending of slurry. The gas reactants ascend to gas-liquid interface 2 while undergoing the reaction, carrying some slurry. They ascend from the opening on the top of reactor vessel 1 and leave the gas-liquid interface 2, and are delivered to the top external circulation apparatus, which is as described above. The liquid materials containing, for example, Ci ₂ -C ₃ o heavy hydrocarbons are discharged as certain liquid products 6 after getting condensed by condenser 4 and conducting liquid-gas separation by gas-liquid separator 5. The worthless portion of the separated gas is discharged as tail gas 8 while the unreacted gas raw materials are used as circulation gas 9 and re-delivered to gas distributor 27 for circulation reaction after being mixed with fresh gas reactant materials and compressed by gas compressor 25. The recyclable liquid materials containing, for example, C ₅ -Ci ₀ light hydrocarbons which are separated from the gas-liquid separator, such as solvents or liquid products, are compressed by circulation pump 10 and heated by optional heater 1 1 , and then delivered to the injectors, and ejected into the reactor vessel 1.

Optionally, the external circulation is conducted for a portion of liquid materials in the slurry materials beneath the gas-liquid interface 2 in the reactor vessel 1 by using the middle external circulation apparatus. Preferably, the middle external circulation and the top external circulation are conducted simultaneously. In particular, the solid components in the slurry are removed by liquid-solid separator 16 in the reactor, and slurry 17 with low solid content after removing solid is delivered to gas-liquid separator 19 by a pressure relief valve 18. The separated gas is discharged as tail gas 20. Liquid- solid separation operation is further conducted for the slurry phase portion in a secondary liquid-solid separator 21 , wherein a portion of separated liquid such as the hydrocarbon products synthesized by a Fischer-Tropsch reaction is drawn as liquid product 22 for further processing and refining treatment. The remaining valuable liquid materials (such as solvents, etc.) is compressed by circulation pump 23 and heated by heater 1 1 , and delivered to the injectors, and ejected upwardly or obliquely upwardly into the reactor vessel 1. The ejecting action further promotes the slurry ascending in the space in the reactor vessel 1 outside of the descending pipe 28.

In another aspect, in the presence of gaseous reactants and injectors, the slurry materials ascend in the space in the reactor vessel 1 and outside of the descending pipe 28 to the surroundings of gas-liquid interface 2. After the gaseous materials from the reaction leave the gas-liquid interface 2, they reach the gas-liquid separation zone 3. The density of the slurry materials increase and enter into the descending pipe 28 from the top opening of the descending pipe 28, flow downwardly under the self-gravity of the slurry and flow out from the opening on the bottom of descending pipe 28. Now the slurry arrives the upward side of gas distributor 27, and ascends again in the space in the reactor vessel and outside of the descending pipe driven by the gas reactants. That is to say, the slurry in the reactor vessel 1 ascends outside of the descending pipe 28, and descends in the descending pipe 28, forming internal circulation of slurry in reactor vessel 1. Meanwhile, the injectors with said height, interval and angles are provided in the reactor vessel. The upward and obliquely upward ejection of liquid materials promotes the ascending of slurry in the space between the inner wall of the reactor vessel and the descending pipes, accelerating the internal circulation. In addition, the middle external circulation apparatus can recycle at least a portion of slurry materials back into the reactor vessel through the external circulation outside the reactor vessel. The liquid (e.g. light hydrocarbons containing C ₅ -C ₁₀ ) that is recycled back to the reactor vessel continues to stir and suspend the slurry. The top external circulation apparatus can recycle at least a portion of gas materials back into the reactor vessel through the external circulation outside the reactor vessel. The gas that is recycled back continues to react. The liquid (e.g. light hydrocarbons containing C ₅ -C ₁₀ ) continues to go back to the reactor vessel, causing stirring and suspending of the slurry. Through the above setting manners, particle suspension, liquid-solid mixing, as well as heat transfer and mass transfer in the slurry-bed reactor are enhanced. The slurry-bed reactions that can be conducted by using this method are selected from the group consisting of a Fischer-Tropsch reaction, a direct coal liquefaction reaction, a synthesis reaction of dimethyl ether from synthesis gas, and a synthesis reaction of methanol from synthesis gas, preferably a Fischer-Tropsch reaction.

When conducting a Fischer-Tropsch reaction by using the reactor as disclosed herein, the slurry is formed by suspending solid catalysts in hydrocarbon oil, the mixed gas of raw gas CO and hydrogen are reacted in the slurry, generating hydrocarbon products and by-products such as a small amount of water and carbon dioxide. Under this situation, the water and gaseous materials in the slurry are removed by the middle external circulation apparatus through the external circulation process. The hydrocarbon products are separated and recovered, and then the remaining slurry is sent back to the injector. The liquid in the top external circulation apparatus is mainly volatile components with low boiling points, such as C ₅ ~Cio light hydrocarbons. In addition, small amount of heavy fractions that are liquid under the reaction temperature and pressure will also enter into the tail gas system due to entrainment of tail gas in the top of the reactor. Finally, very small amount of heavy fractions will still enter the external circulation liquid flow portion (engineering terminology, flow of substances) after despumation, condensation, phase splitting and dehydration.

The slurry-bed Fischer-Tropsch synthesis reactor is a complete reaction system, and it is one of the effective means to improve the particle suspension and liquid-solid mixing effect and enhance turbulent by the liquid circulation. In the slurry-bed reactor of the present invention, descending pipes conducive to internal slurry circulation are provided.

By providing descending pipes and injectors in the present invention, the slurry materials ascend outside of the descending pipes and descend in the descending pipes in the presence of injectors, and thus forming the circulation in and outside of the descending pipes, i.e. in the reactor vessel. The present invention realize optimized turbulence effects, enhancing gas-liquid and liquid-solid stirring, and improving particle suspension and liquid-solid circulation by spraying the materials into the reactor vessel through the injectors after being circulated by the top external circulation apparatus and the middle external circulation apparatus, preferably by the position and angle of the injectors. Preferably, the ejecting kinetic energy per unit volume of the slurry is only necessary to maintain the turbulence required for the reaction. Otherwise, excessive ejecting kinetic energy will result in excessive energy consumption. Meanwhile, it may also cause mechanical vibration of the internal components of the reactor. The external circulation liquid is ejected into the slurry in the reactor from the injectors provided according to specific angles and positions. The ejecting kinetic energy per unit volume of or liquid is 0.001-0.05 W/m ³ , preferably 0.002-0.005 W/m ³ for example at least 0.001 W/m ³ , 0.002 W/m ³ , 0.003 W/m ³ , 0.004 W/m ³ , 0.005 W/m ³ or 0.008 W/m ³ , or for example no more than 0.01 W/m ³ , 0.02 W/m ³ , 0.03 W/m ³ , 0.04 W/m ³ or 0.05 W/m ³ .